The present invention relates generally to broadcast radios; and, more particularly, it relates to broadcast radios employing a common front-end circuitry that is operable for multiple operating modes including both frequency modulation (FM) and amplitude modulation (AM) modes.
Conventional broadcast radios that employ a common intermediate frequency to both amplitude modulation (AM) and frequency modulation (FM) signals typically operate at a high intermediate center frequency. For example, certain conventional broadcast radios employing a common intermediate frequency operate substantially at 10.7 MHz. This high frequency operation is desired for FM signal processing, in discrete format because relatively cheap, ceramic filters, and coils are available for processing FM signals. Relatively expensive crystal filters are required for AM signal processing at these high frequencies. While the perceptual quality and performance of the AM signal processing is still achievable at high intermediate frequencies, there is an associated penalty in cost. Further, for integrated solutions, this cost is due to, among other things, the high precision required for components to perform AM signal processing on the silicon die.
There is desirability in using a common intermediate frequency broadcast radio front end, but many of the advantages gained in using a common front end are outweighed by the associated penalties to be paid in required component precision and cost of the device. In addition, in an integrated solution, the signal to noise ratio is difficult to maintain while operating at an elevated intermediate. Those having skill in the art of signal processing will appreciate the difficulty of performing precision signal processing at such elevated frequency ranges.
Further limitations and disadvantages of conventional and traditional systems will become apparent to one of skill in the art through comparison of such systems with the present invention as set forth in the remainder of the present application with reference to the drawings.